TABLE OF CONTENT – SECTION I

ABSTRACT............................................................................................................................. x

SECTION I MOVING BED BIOFILM REACTOR VERSUS BIOLOGICAL AERATED FILTRATION......................................................................................... XII

CHAPTER 1.0 INTRODUCTION AND BACKGROUND .........................................1

CHAPTER 2.0 OBJECTIVES..................................................................................3

CHAPTER 3.0 LITERATURE REVIEW...................................................................4

3.1 The Moving Bed Biofilm Reactor.............................................................................. 4 3.1.1 Factors Affecting Performance ............................................................................. 5 3.1.2 Organic carbon removal...................................................................................... 10 3.1.3 Nitrification......................................................................................................... 10

3.2 Biological Aerated Filter (BAF)............................................................................... 11 3.2.1 Performance ........................................................................................................ 13 3.2.2 BOD5 removal..................................................................................................... 14 3.2.3 Nitrification......................................................................................................... 14

3.3 Modeling Biofilm Systems........................................................................................ 18

CHAPTER 4.0 MATERIALS AND METHODS......................................................24

4.1 Biotreatment System Overview ............................................................................... 24

4.2 Wastewater Characterization and modification .................................................... 25

4.3 Reactor Design and Operation. ............................................................................... 26 4.3.1 MBBR................................................................................................................. 26

4.3.1.1 Stimulus – Response Study (Tracer Study). ................................................... 31 4.3.2 BAF..................................................................................................................... 32

4.4 Kinetic And Stoichiometric Parameter Determination......................................... 35

4.5 Analytical methods.................................................................................................... 37

4.6 Development of the MBBR model ........................................................................... 39

CHAPTER 5.0 RESULTS AND DISCUSSION......................................................41

5.1 Virginia Tech Sewage Characterization ................................................................. 41

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5.1.1 Initial Wastewater Quality Screening ................................................................. 41

5.2 Stimulus - Response (Tracer) Study....................................................................... 46

5.3 MBBR performance.................................................................................................. 49 5.3.1 BOD5 Removal ................................................................................................... 49 5.3.2 TSS Removal ...................................................................................................... 53 5.3.3 Ammonia Oxidation............................................................................................ 54 5.3.4 MBBR Performance Summary ........................................................................... 56

5.4 Biological Aerated Filters......................................................................................... 57 5.4.1 BOD5 removal ..................................................................................................... 57 5.4.2 TSS Removal ...................................................................................................... 59 5.4.3 Ammonia Oxidation............................................................................................ 61 5.4.4 BAF Backwashing .............................................................................................. 62 5.4.5 BAF Performance Summary............................................................................... 63

5.5 MBBR Kinetic and Yield Study and Model ........................................................... 65 5.5.1 Biofilm thickness. ............................................................................................... 65 5.5.2 Biofilm density.................................................................................................... 65 5.5.3 Substrate utilization rate ..................................................................................... 66 5.5.4 Yield.................................................................................................................... 66 5.5.5 Pseudo – analytical model and results ................................................................ 66 5.5.6 ISO Area Demand for MBBR versus BAF......................................................... 67

CHAPTER 6.0 CONCLUSIONS AND RECOMMENDATIONS.............................68

6.1 MBBR......................................................................................................................... 68

6.2 BAF Reactor .............................................................................................................. 69

6.3 Recommendations ..................................................................................................... 69

CHAPTER 7.0 REFERENCES..............................................................................70

CHAPTER 8.0 APPENDICES ...............................................................................74

APPENDIX A1 - GENERAL............................................................................................... 74 BOD Supplement (‘Candy’) Preparation............................................................................ 74 Media surface area relative to reactor volume calculation. ................................................ 75 Wastewater characteristics data .......................................................................................... 76

APPENDIX A2 - MBBR DATA .......................................................................................... 77 MBBR BOD5 data............................................................................................................... 78 MBBR CBOD5 data ............................................................................................................ 79 67 % media volume MBBR, BOD5 and TSS data.............................................................. 80 MBBR SBOD5 data............................................................................................................. 81

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MBBR TSS Data ................................................................................................................ 82 MBBR Ammonia Data ....................................................................................................... 84

APPENDIX A3 – BAF DATA.............................................................................................. 85 Summary of results for 1st and 2nd stage effluent wastewater characteristics in BAF........ 85 First column BAF TBOD5 .................................................................................................. 86 First and Second Column BAF TBOD5.............................................................................. 87 First and Second Column BAF TSS DATA....................................................................... 89 First and Second Column BAF AMMONIA DATA.......................................................... 91

APPENDIX A4 - BAF/ MBBR NITRATE DATA............................................................. 92

APPENDIX A5 - KINETIC AND STOICHIOMETRIC EXPERIMENT DATA.......... 93 Yield Data ........................................................................................................................... 93 Substrate Utilization Rate Data........................................................................................... 93

SECTION II - SULFIDE-INDUCED CORROSION IN ANAEROBIC DIGESTER GAS PIPING.....................................................................................................................94

CHAPTER 1.0 INTRODUCTION AND BACKGROUND .......................................95

1.1 Background ............................................................................................................... 95

1.2 Introduction............................................................................................................... 97

CHAPTER 2.0 OBJECTIVES................................................................................98

CHAPTER 3.0 LITERATURE REVIEW.................................................................99

3.1 Fate of sulfur in Bioreactors .................................................................................... 99

3.2 Corrosion mechanism............................................................................................. 102

3.3 Corrosion Measurement......................................................................................... 105

4.1 Reactor setup........................................................................................................... 106

4.2 Operation and Maintenance .................................................................................. 111

4.3 Sample preparation and testing............................................................................. 112

4.4 Precision of Corrosion Measurement.................................................................... 114

CHAPTER 5.0 RESULTS AND DISCUSSION....................................................115

5.1 Laboratory Experiment I Reactor Performance ................................................. 115

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5.2 Corrosion ................................................................................................................. 119

5.3 Field Analysis of solid precipitate from Digester Gas Pipe at PFRWTF........... 131

CHAPTER 6.0 SUMMARY AND CONCLUSIONS..............................................133

CHAPTER 7.0 RECOMMENDATIONS...............................................................133

CHAPTER 8.0 APPENDICES .............................................................................134 Appendix B1 Classification of reactive environment based on H2S(g) concentration. .. 134 Appendix B2. MLSS/ MLVSS Data.............................................................................. 134 Appendix B3. Field gas composition trends .................................................................. 136 Appendix B4. Primary Digester Influent , Effluent Sulfate, Sulfite and Sulfide Data. ... 136 Appendix B4. Primary Digester Influent , Effluent Sulfate, Sulfite and Sulfide Data. .... 137 Appendix B5. pH Data................................................................................................... 138 Appendix B6. Corrosion Data........................................................................................ 139

CHAPTER 9.0 REFERENCES:...........................................................................140

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TABLE OF FIGURES – SECTION I

Figure 1.1 MBBR carrier elements by Kaldnes ................................................................. 5 Figure 1.2(a) Different MBBR configurations for BOD5 removal. ................................... 7 Figure 1.2(b) Different MBBR configurations for nitrification.......................................... 8 Figure 1.3 Ideal biofilm structure as it relates to substrate penetration profile................ 19 Figure 1.4 Schematic of MBBR system with 40 % media (same configuration for 67 %

media volume).................................................................................................................. 27 Figure 1.5 Schematic of 2-stage MBBR with 40 % media volume. ................................ 29 Figure 1.6 Schematic of MBBR with 40 % media operated with return sludge.............. 30 Figure 1.7 A schematic diagram of 1st and 2nd stage BAF reactor. .................................. 34 Figure 1.8 (A) Sliced MBBR media with biofilm.(B) Metric scale used to determine

biofilm thickness. ............................................................................................................. 37 Figure 1.9 Single stage, 40 % media volume MBBR modeled as 3 CSTRs in series...... 39 Figure 1.10 Plot of suspended solids versus time in settling experiment on VT sewage. . 43 Figure 1.11 TBOD5, CBOD5 and DOC trends in VT sewage............................................ 44 Figure 1.12 Influent TBOD5 and DOC correlation for VT sewage. ................................... 45 Figure 1.13 F-Curve measured during replicate tracer experiments for a single MBBR

with 40 % media volume, E-Curves derived from F- Curves. ......................................... 48 Figure 1.14 Influent and effluent BOD5 trends in MBBR with 40 % media volume. ....... 49 Figure 1.15 Plot of BOD5 trends obtained with 67 % media volume reactors................... 51 Figure 1.16 Plot of BOD5 loading rate versus removal rate for 40 % media volume. ....... 52 Figure 1.17 Influent and effluent TSS concentration trends with 40 % media volume. ... 53 Figure 1.18 Ammonia trends in MBBR with 40 % media volume................................... 55 Figure 1.19 BOD5 trends in 1st and 2nd stage BAF columns. ............................................ 58 Figure 1.20 Influent and 2nd stage effluent TSS concentrations in BAF............................ 60 Figure 1.21 Influent, 1st and 2nd stage effluent ammonia concentration in BAF ............... 62 Figure 1.22 Plot of BOD5 mass loading rate versus removal rate for 1st and 2nd column

BAFs. 64

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LIST OF FIGURES – SECTION II

Figure 2.1 Mechanism of sulfide generation and corrosion in sewers........................... 103 Figure 2.2. Schematic (A) and photograph (B) of experimental setup I ......................... 107 Figure 2.3 Schematic (A) and photograph (B) of experimental setup II........................ 108 Figure 2.4 Percentage composition of digester gas components.................................... 116 Figure 2.5 MLSS / MLVSS trends in primary digester effluent. ................................... 117 Figure 2.6 pH trends in primary digester effluent. ........................................................ 118 Figure 2.7 Appearance of experimental and control metals 13 days (A) and 62 (B) days

after the start of the experiment...................................................................................... 121 Figure 2.8 Influent sulfate concentration and effluent total dissolved sulfate, sulfite and

sulfide (TDSSS). ............................................................................................................ 123 Figure 2.9 Hydrogen sulfide gas concentrations in experimental and control lines during

experiment II. ................................................................................................................. 124 Figure 2.10 Cumulative percentage change in weight of pipes during experiments I and II

125 Figure 2.11 Cumulative percentage change in weight of iron shavings during experiments

I and II 126 Figure 2.12 Rate of Corrosion in experimental metal iron and shaving. ......................... 127 Figure 2.13 The percentage reduction in influent sludge sulfate concentration and total

dissolved sulfate, sulfite and sulfide (TDSSS) as a fraction of influent sulfate concentration .................................................................................................................. 129

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LIST OF TABLES – SECTION I

Table 1.1 Typical design values for KMT reactors at 15o Ca ............................................... 8 Table 1.3 Ammonia removal using biological aerated filters for wastewater treatment a. . 17 Table 1.4 Kinetic parameters used in pseudo analytical model.......................................... 20 Table 1.5 Relationship between dimensionless variables and dimensioned variables. ...... 23 Table 1.6 Wastewater characteristics during recess periods............................................... 41 Table 1.7 Wastewater characteristics during school periods. ............................................. 41 Table 1.8 Influent wastewater characteristics obtained during the reactor study. .............. 46 Table 1.9 Summary of results from tracer study on a single MBBR with 40 % media

volume 47 Table 1.10 Biofilm thickness for the MBBR reactors used during the study. .................. 65 Table 1.11 ISO Surface area demand for MBBR versus BAF. ........................................ 67

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LIST OF TABLES – SECTION II

Table 2.1 Free energy changes for biologically-mediated sulfate reduction and methane production....................................................................................................................... 100

Table 2.2 Percentages of hydrogen sulfide and HS- and solubility of hydrogen sulfide as a function of pH. ............................................................................................................... 101

Table 2.3 Solubilty Data for Selected Metal Sulfides....................................................... 130

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